The present invention generally relates to an adjusting mechanism and more particularly, to a fine adjusting mechanism for a preset type tuner which employs a clutch system for use, for example, in a television receiver.
Conventionally, as a fine adjusting mechanism for a preset type tuner of the above described kind, there has been proposed, for example, an arrangement as shown in FIG. 1, which includes a fine adjusting shaft 1 rotatably supported by a tuner frame 2. A transmission gear 6 is rotatably mounted on a slider 5 and urged by a spring 4 in the direction indicated by an arrow Ar2 so as to be spaced from the fine adjusting shaft 1. A coil spring S is fitted, using its spring force, onto the shaft 1 at a position where the slider 5 is externally fitted over the shaft 1 as is most clearly shown in FIG. 2(a). The slider 5 and the transmission gear 6 are mounted to be slidable between the tuner frame 2 and a front plate 3 thereof back and forth in the directions indicated by arrows Ar1. Accordingly, the slider 5 and the transmission gear 6 are slidable in a direction which is perpendicular to the axial direction of the shaft 1.
Upon rotation of the fine adjusting shaft 1, the coil spring S rotates simultaneously with the fine adjusting shaft 1 as shown in FIG. 2(b), and a biasing member Sa provided on the coil spring S displaces the slider 5 in a direction of an arrow Ar3 so as to bring gears 6a and 6b provided at opposite ends of the transmission gear 6 into engagement with a gear 1a a of the fine adjusting shaft 1 and a gear 7 having a threaded portion for local oscillation frequency adjustment.
Incidentally, for the fine adjusting mechanism of the preset type tuner, there has also been employed, besides the clutch system as described so far, a push system mechanism as shown in FIG. 3, which is so arranged that, by pivotally supporting a lever 13 at a support portion 12a provided on a front frame 12 of a tuner frame 11, the lever 13 is urged, by a spring force of a spring 14, in a direction opposite to the direction for depressing a fine adjusting shaft 15 into the front frame 12, so that, upon depression of said shaft 15 into the front frame 12, the lever 13 is pivoted so as to bring gears 16a and 16b of a transmission gear 16 rotatably mounted on said lever 13, into engagement with a gear 15a provided on the fine adjusting shaft 15 and a gear 17 having a threaded portion respectively.
As is clear from a comparison between the fine adjusting mechanism of the preset type tuner employing the clutch system in FIG. 1 and that of the tuner of the push system in FIG. 3, there are only few parts which can be commonly used therebetween, and if it is intended to manufacture the push type tuner together with the clutch type tuner, the number of parts exclusive for each type of the tuners is undesirably increased.
Moreover, in the fine adjusting mechanism for the preset type tuner of FIG. 1, the acting point of the biasing member Sa of the coil spring S with respect to the slider 5 is limited to one point, and thus, an undue force tends to be applied to the slider 5, coil spring S, etc., while it is necessary to provide a large opening (not particularly shown) in the tuner frame 2 for ensuring positive sliding and assembling of the slider 5, thus inviting such a problem that an unnecessary radiation through said opening is undesirably increased.